Plastic tubing connector

ABSTRACT

There is disclosed a connector for tubing made from plastic having cold flow characteristics. A tubular insert is placed in the end of the plastic tubing. A tubular sleeve is positioned over the tube. Elastomeric O-rings are mounted on the tubing at the end of the sleeve. An internally threaded tubular coupling member is threaded onto the plastic tubing, compressing the Orings between the member and the end of the sleeve. The coupling member is secured to the sleeve to retain the O-rings in their compressed state.

United States Patent Reynolds et al.

[54] V PLASTIC TUBING CONNECTOR [72] Inventors: Frank L. Reynolds,Monroe; Alfred C. Langer, Brookfield; Ellsworth Tweedie, Milford, all ofConn.

[73] Assignee: Frigitronics of Conn., Inc., Shelton, Conn.

[22] Filed: Sept. 9, 1970 [21] Appl. N0.: 70,751

52 us. Cl. ass/244, 285/248 [51] Int. Cl. ..F16l33/00 [58] Field ofSearch ..285/248, 246, 244

[56] References Cited UNITED STATES PATENTS 3,120,966 2/1964 Lyon..285/247 X 3,476,414 11/1969 Condrac ..285/354 X 51 3,690,704 [451Sept. 12,1972

3,193,310 7/1965 l-Iildner ..285/248 X FOREIGN PATENTS OR APPLICATIONS121,840 1/1919 Great Britain ..285/248 Primary Examiner-Andrew V.Kundrat Attorney-Buckles and Bramblett [57] ABSTRACT There is discloseda connector for tubing made from plastic having cold flowcharacteristics. A tubular in- 9 Claims, 5 Drawing Figures 1 PLASTICTUBING CONNECTOR BACKGROUND OF THE INVENTION It is often required to useplastic tubing for the delivery of relatively high pressure gas. In somecircumstances the tubing must satisfy other requirements than theability to withstand high pressure. For example, one type ofcryosurgical device employs high pressure gas for cooling by theJoule-Thomson effect. The delivery system for such a device should belightweight and flexible. In addition, it should be chemically inert andcapable of withstanding autoclaving. Two of the plastics which are mostsuitable for tubing of this nature are polytetrafluoroethylene andnylon. Unfortunately, however, both plastics have a definite cold flowtendency under high compression. Accordingly, users of such tubing haveexperienced a high rate of failures. Due to the high pressures of thegas, e.g., l,0002,000 psi, the couplings must be very tight and theplastic tends to flow therefrom, eventually causing the couplings tofail.

It is a primary object of the present invention to provide an improvedconnector for plastic tubing. Other objects are to provide such aconnector which substantially overcomes the problems created by the coldflow characteristics of plastic; which is capable of withstanding highpressure; and which is relatively simple and uncomplicated. The mannerin which these objectives are achieved will be apparent from thefollowing description and appended claims.

SUMMARY OF THE INVENTION In accordance with the invention, there isprovided a connector for plastic tubing which comprises a relativelyrigid tubular insert in the end of the tubing. A tubular sleeve ispositioned over the tubing. Tubular coupling means is provided whichengages the plastic tubing and the tubular sleeve and defines aninternal shoulder axially spaced from the sleeve. Elastomeric means areprovided which encircle the tubing intermediate the shoulder and tubularsleeve and are compressed therebetween.

BRIEF DESCRIPTION OF THE DRAWING DESCRIPTION OF THE PREFERREDEMBODIMENTS With particular reference to the drawing, there isillustrated a connector for the end of a section of plastic tubing 10.While the actual dimensions are not critical and form no part of thisinvention, the external diameter of such tubing for use with acryosurgical instrument may be, for example, .1 inch.

illustrating Into the end of the tubing 10 is inserted a tubularstainless steel insert 12. A tubular metal sleeve 14 is then slid overthe end of the tubing. The end of sleeve 14 defines an annular flange16. Next, a plurality of elastomeric O-rings 18 are also slid over theend of the tubing 10. A commercially available helical coil 20 is thenmounted on the tubing. This is a coil of the type commonly used as aninsert for forming internal threads and the wire forming the coil has adiamond shaped cross section. In this application, however, it isapplied externally of the end of tubing 10. Its sizeis such that itsnormal internal diameter is smaller than the external diameter of thetubing. By use of commercially available equipment, the coil is expandedand, in

its expanded condition, is positioned over the end of the tubing 10 andpermitted to collapse. It then tightly engages the end of the tubing.

A coupling member 22 is the last element to be added. In externalappearance, the coupling member 22 is cylindrical as will be seen fromFIG. 2. However it will be noted from FIG. 3 that approximatelyone-third of its length comprises a relatively thin wall 24 whichterminates at an inner shoulder 26. Extending from shoulder 26 is aportion with internal threads 28. This portion also terminates at ashoulder 30, and the remaining length of the coupling member 22 has adifferent internal thread 32.

The coupling member 22 is positioned over the end of tubing 10 andthreaded thereon. The internal threads 28 engage the convolutions ofcoil 20, causing the coil to be compressed more tightly into the plastictubing 10. When coupling member 22 has been fully threaded onto coil 20as shown in FIG 3, the flange 16 of sleeve 14 is forced into the end ofcoupling member 22, compressing the elastomeric O-rings 18 betweenshoulder 26 and flange 16. The thin walled end of coupling member 22 isthen crimped over the flange 16 as at 34, thereby retaining the O-ringsin a compressed condition. Thereafter, a suitably threaded conduit 36may be threaded into the coupling member 22.

It will be seen from the foregoing that coupling member 22 is, ineffect, threadedl on the tubing 10 through the medium of the coil 20,thus providing an axial grip on the tubing. As the plastic tends to fiowoutward from this region, the elastomeric O-rings 18 maintain a constantsealing pressure thereon, preventing failure of the connection.

In FIGS. 4 and there is illustrated a modified ver-' sion of theinvention, which is quite similar to that of FIGS. 1-3. Accordingly,similar reference numerals are used for similar parts. The primarydistinction between the two modifications is that in the FIG. 4 and FIG.5 version, the helical coil is omitted. In place of coupling member 22,there is provided a modified member 22 in which the inner threads 28 areof a smaller diameter. This member is actually threaded onto the surfaceof the plastic tubing 10 to compress O-rings 18, the 7 threads 28partially biting into the surface of the plastic tubing, as illustratedin FIG. 4. Prior to the insertion of stainless steel insert 12, therewas threaded through it a small wire 38 having at its end a ball 40 ofslightly greater diameter than the internal diameter of the steel insert12. After assembly, a force is exerted on wire 38, pulling the ball 40through the steel insert 12, thereby causing it to expand as shown inFIG. 4. When the insert is fully expanded, the plastic material of thetubing substantially fills the threads 28 as will be seen in FIG. 5 andthe O-rings' 18 are further compressed until each is almost square incross section.

it will be apparent to those skilled in the art that other variationsand modifications may also be made in this invention. Accordingly, theforegoing disclosure is to be construed as illustrative only, ratherthan limiting. This invention is limited only by the scope of thefollowing claims.

We claim:

1. A connector for plastic tubing which comprises: a relatively rigidtubular insert in the end of said tubing; a tubular sleeve over saidtubing; a helical coil tightly engaging said tubing; an internallythreaded tubular coupling member threaded onto said coil and defining aninternal shoulder axially spaced from said sleeve; and elastomeric meansencircling said tubing intermediate said shoulder and tubular sleeve andcompressed therebetween.

2. The connector of claim 1 wherein said elastomeric means comprises aplurality of O-rings.

3. The connector of claim 1 wherein said sleeve defines a radiallyextending flange and said tubular coupling member engages said flange.

4. A connector for plastic tubing which comprises: a relatively rigidtubular insert in the end of said tubing; a tubular sleeve over saidtubing defining a radially extending flange; a tubular coupling memberengaging said plastic tubing with its end crimped over said flange anddefining an internal shoulder axially spaced from said sleeve; andelastomeric means encircling said tubing intermediate said shoulder andtubular sleeve and compressed therebetween.

5. The connector of claim 4 wherein said insert is a metal tube havingan external diameter greater than the normal internal diameter of saidtubing.

6. The connector of claim 5 wherein said elastomeric means comprises aplurality of O-rings.

7. The connector of claim 5 wherein said sleeve defines a radiallyextending flange and said tubular coupling member engages said flange.

8. A connector for plastic tubing which comprises: a tubular metalinsert in the end of said tubing having an external diameter greaterthan the normal internal diameter of said tubing; a tubular sleeve oversaid tubing defining a radially extending flange; a tubular couplingmember engaging said plastic tubing with its end crimped over saidflange and defining an internal shoulder axially. spaced from saidsleeve; and elastomeric means encircling said tubing intermediate saidshoulder and tubular sleeve and compressed therebetween.

9. A connector for plastic tubing which comprises: a tubular metalinsert in the end of said tubing having an external diameter greaterthan the normal internal diameter of said tubing; a tubular sleeve oversaid tubing; internally threaded tubular coupling means threadedlyengaging the surface of said plastic tubing, engaging said tubularsleeve, and defining an internal shoulder axially spaced from saidsleeve; and elastomeric means encircling said tubing intermediate saidshoulder and tubular sleeve and compressed therebetween.

1. A connector for plastic tubing which comprises: a relatively rigidtubular insert in the end of said tubing; a tubular sleeve over saidtubing; a helical coil tightly engaging said tubing; an internallythreaded tubular coupling member threaded onto said coil and defining aninternal shoulder axially spaced from said sleeve; and elastomeric meansencircling said tubing intermediate said shoulder and tubular sleeve andcompressed therebetween.
 2. The connector of claim 1 wherein saidelastomeric means comprises a plurality of O-rings.
 3. The connector ofclaim 1 wherein said sleeve defines a radially extending flange and saidtubular coupling member engages said flange.
 4. A connector for plastictubing which comprises: a relatively rigid tubular insert in the end ofsaid tubing; a tubular sleeve over said tubing defining a radiallyextending flange; a tubular coupling member engaging said plastic tubingwith its end crimped over said flange and defining an internal shoulderaxially spaced from said sleeve; and elastomeric means encircling saidtubing intermediate said shoulder and tubular sleeve and compressedtherebetween.
 5. The connector of claim 4 wherein said insert is a metaltube having an external diameter greater than the normal internaldiameter of said tubing.
 6. The connector of claim 5 wherein saidelastomeric means comprises a plurality of O-rings.
 7. The connector ofclaim 5 wherein said sleeve defines a radially extending flange and saidtubular coupling member engages said flange.
 8. A connector for plastictubing which comprises: a tubular metal insert in the end of said tubinghaving an external diameter greater than the normal internal diameter ofsaid tubing; a tubular sleeve over said tubing defining a radiallyextending flange; a tubular coupling member engaging said plastic tubingwith its end crimped over said flange and defining an internal shoulderaxially spaced from said sleeve; and elastomeric means encircling saidtubing intermediate said shoulder and tubular sleeve and compressedtherebetween.
 9. A connector for plastic tubing which comprises: atubular metal insert in the end of said tubing having an externaldiameter greater than the normal internal diameter of said tubing; atubular sleeve over said tubing; internally threaded tubular couplingmeans threadedly engaging the surface of said plastic tubing, engagingsaid tubular sleeve, and defining an internal shoulder axially spacedfrom said sleeve; and elastomeric means encircling said tubingintermediate said shoulder and tubular sleeve and compressedtherebetween.